So I'm having a problem with exporting to Unity using clipping masks. Everything works fine in spine, but once in unity there's an issue where some layers are shown outside of the mask that were set to be inside of it while using spine. I narrowed the problem down to the "set a slot after which clipping ends" option in spine. While it works as intended in Spine, it appears to have the behavior to end the clipping mask AT the specified slot, rather than after it, once exported to Unity (hence why only a few specific layers were refusing to be masked). My current work around is to make empty slots in order to remedy this, but figured it would be worth bringing to your attention for a potential future fix.
thanks!